The invention generally relates to medical instruments. More specifically, the invention relates to medical instruments, having a shaft which has an outer shaft and an inner shaft, wherein the outer shaft encloses the inner shaft, and wherein the inner shaft is rotatable with respect to the outer shaft.
Medical instruments of the type initially described are used, for example, in minimally invasive surgery during a laparoscopic procedure to remove diseased tissue or also to atrophy previously sectioned tissue. For this purpose, a distal end region of the shaft of the medical instrument is inserted into a body cavity of a patient, on which corresponding gripping instruments, electrodes or the like are arranged. The shaft of the medical instrument is usually designed in two parts and has an inner shaft rotatable about the longitudinal axis of the medical instrument, which is housed in an outer shaft. The operation instruments are accordingly arranged on the distal end region of the inner shaft. The operation instruments are put in a position favourable for the procedure only after the shaft has been inserted into the operation area by rotation of the inner shaft relative to the outer shaft around the longitudinal axis of the medical instrument.
A medical instrument known from CA 2 212 768 A in form of a morcellator has an outer shaft, which encloses an inner shaft rotatable relative to it and is connected, such that it is rotationally fixed, to a proximal end of the handle of the medical instrument. The outer shaft extends as far as a distal end of the handle, while the inner shaft extends through the handle as far as a proximal end of the handle. A motor housed in the handle is connected, such that it is rotationally fixed, via a tappet element to the inner shaft. The tappet element has a gearwheel drive, which is connected, such that it is rotationally fixed, to a region of the inner shaft, arranged proximally to the proximal end of the outer shaft in order to rotate the inner shaft about the longitudinal axis.
Other medical instruments are generally known which have only an outer shaft, which is connected, such that it is rotationally fixed, to a handle. The outer shaft of the known instrument extends into the interior of the handle, and its proximal end region is screwed to the handle in the handle interior via a nut. The handle of the medical instrument can, for example, be a handle already available and normally capable of being used for operations in the area of minimally invasive surgery.
If it is planned to further develop such a medical instrument to the extent where, in addition to the outer shaft, it has an inner shaft inside the outer shaft which is rotatable about the longitudinal axis, the technical problem arises as to how corresponding torque transmission mechanics of the instrument could be designed which would allow relative rotation of the inner and outer shaft with simultaneous screwing of the outer shaft to the handle inside the handle.
A conceivable configuration of such a further developed medical instrument is based on arranging magnets on the actuator and in the proximal end region of the inner shaft, thereby transferring the rotary movement of the actuator to the inner shaft without contact through the proximal end region of the outer shaft.
With this configuration of the torque transmission mechanics there is the disadvantage, however, with this type of torque transmission of only minimal force transfer made to the inner shaft.
In a further configuration of the developed instrument the proximal end region of the outer shaft, which is arranged inside the handle, could be interrupted about its entire circumference in two parts, and the actuator could directly engage on the inner shaft in the vicinity of this interruption between the two parts of the outer shaft.
In this embodiment of the medical instrument it is a disadvantage, however, for both parts of the proximal end region of the outer shaft to have to be connected, such that it is rotationally fixed, to the handle.
Yet another configuration of the further developed medical instrument could be based on guiding the inner shaft completely through the handle and arranging the actuator on the proximal side outside the handle directly on the inner shaft. The outer shaft would hereby be housed in the handle interior and connected, such that it is rotationally fixed, to the handle.
This configuration of the medical instrument does however have the disadvantage of the medical instrument not being able to be operated with one hand by a user, since the actuator is arranged on the proximal side of the handle.